Microfluidic devices for driving fluids are known in the art. These devices generally comprise a circuitry or flow network for driving fluids such as reagents to a particular reaction area or chamber. Detection of the foregoing reaction is usually burdensome since standard detection techniques cannot be used given the relative complexity of such microfluidic devices.
Microarrays involve bimolecular interactions where one partner is in solution and the other one is attached to a surface (Howbrook et al., 2003 Drug Discovery Today, 8:642-651; Kusnezow and Hoheisel, 2003, J. Mol. Recogni. 16:165-176). For positive interaction to take place, there should be an encounter between the solution phase partner and the surface phase partner. Such an encounter could be driven by several phenomena such as diffusion, electrostatic attraction, magnetic confinements, and forced or directed flow. In most conventional microarrays, diffusion is the major driving force. However, this is a slow process requiring between 3 to 16 hours (Maughan et al., 2001, J. Pathol., 195:3-6). A system using electrostatic attraction demonstrated faster hybridization on arrays made on electrodes (U.S. Pat. No. 6,099,803). However, in these systems low ionic strength solutions must be used. Wang et al. demonstrated that dynamic DNA hybridization can be achieved by flowing analytes through a microarray surface using an especially designed array combined with microfluidic circuitry (Wang et al., 2003, Anal. Chem., 75:1130-1140).
Over the last decade, DNA microarrays have become a powerful tool for genomic and proteomic research. Microarrays allow up to several thousands of nucleic acid probes to be spotted onto very small solid supports (millimeter scale); generally glass slides (Bryant et al., 2004, Lancet Infect. Dis., 4:100-111; Heller, 2002, Annu. Rev. Biomed. Eng., 4:129-153; Maughan et al., 2001, J. Pathol., 195:3-6; Pirrung, 2002, Angew. Chem. Int. Ed., 41:1276-1289).
Recent efforts were conducted to adapt the microarray technology for rapid identification of biomolecules using signal transduction; the biomolecule binds to a specific probe attached onto the solid support (Mikhailovich et al., 2001, J. Clin. Microbiol., 39:2531-2540; Chizhikov et al., 2001, Appl. Environ. Microbiol., 67:3258-3263; Chizhikov et al., 2002, J. Clin. Microbiol., 40:2398-2407; Wang et al., 2002, FEMS Microbiol. Lett., 213:175-82; Loy et al., 2002, Appl. Environ. Microbiol., 68:5064-5081; Wilson et al., 2002, Mol. Cell. Probes, 16:119-127). Such rapid identification is important for diagnostic and forensic purposes, for food and water testing as well as for rapid pathogen detection and identification. Classical-DNA microarrays such as Affymetrix's Genechip™ or custom glass-slide technology require hybridization times of up to 18 hours for nucleic acids detection. These methods are thus not fit for rapid molecular testing.
To speed up the hybridization reaction, several approaches to provide active hybridization systems, or to increase the hybridization dynamics in passive systems have been developed. Electric fields have been used to attract nucleic acid analytes onto capture probes immobilized on electrode surfaces (U.S. Pat. Nos. 6,245,508; 6,258,606; Weidenhammer et al., 2002, Clin. Chem., 48:1873-1882; Westin et al., 2001, J. Clin. Microbiol., 39:1097-1104). Such a system allows for rapid DNA hybridization (in the order of minutes), but requires expensive hybridization equipment and reader devices.
Flow-through systems, where targets flow over the probes, increase the probability of interactions between the analyte and the probe. Wang et al. disclosed the use of microfluidic circuitries associated with microarrays, and demonstrated that smaller hybridization chambers, in combination with flow-through hybridization, enhanced the hybridization kinetics (Wang et al., 2003, Anal. Chem., 75:1130-1140).
Microfluidics is an emerging technology allowing to move very small volumes in microscopic tubing adapted for different applications. Channels and chambers are microfabricated in a base of silicon, hard plastic or soft elastomers such as PDMS (Poly-dimethylsiloxane) (Bousse et al., 2000, Annu. Rev. Biophys. Biomol. Struct.; 29:155-181; Anderson et al., 2000, Anal. Chem.; 72:3158-3164). Fluid propulsion and control valves are designed to allow sequential displacement of liquids into the various segments of the circuits. Numerous microfluidic systems have been set-up for hybridization purposes using different microfluidic technologies (Wang et al., 2003, Anal. Chem., 75:1130-1140; Lenigk et al., 2002, Anal. Biochem., 311:40-49; Fan et al., 1999, Anal. Chem. 71:4851-4859). However, these technologies are complex, expensive to prototype, and require custom made systems for the arraying of bioprobes and detection of hybridization signals Noerholm et al. developed a microfluidic circuit engraved in a plastic polymer (Noerholm et al., 2004, LabChip 4:28-37). The microarray was spotted directly onto the plastic surface of the engraved hybridization chamber. Thus, this system requires a special microarray support, and consequently, cannot be read on commercially available array scanners. Spute and Adey (WO 03/05248 A1) described a three-dimensional fluidic structure for hybridization, but this system requires several layers of microfluidic structures.
Microarrays constitute a promising technology for the rapid multi-detection of nucleic acids with potential applications in all fields of genomics including microbial (e.g. bacteria, viruses, parasites and fungi) human, animal and plant genetic analysis. Currently, hybridization protocols on microarrays are slow, need to be performed by skilled personnel, and are therefore not suited for rapid diagnostic applications such as point of care testing. The merging of microfluidic and microarray technologies provides an elegant solution to automate and speed up microarray hybridization and detection. Such an association has already been described but requires a complex and expensive microfluidic platform.
There thus remains a need to provide an improved microfluidic flow cell, an improved microfluidic device, an improved microfluidic method and an improved microfluidic system.
There thus remains a need for a rapid, efficient, reliable and low cost method for performing microarray analyses.
The present invention seeks to meet these and other needs.